In Automatically Switched Optical Networks (ASON) and Generic Multi-Protocol Label Switching (GMPLS) networks, in-band control plane communication is used for routing and signaling. The integrity of the in-band communication channel is often dependent on the state of the routed circuit that carries the in-band communication control signal. This is true, for example, in the case of a G.709 compliant Optical Data Unit (ODUk) circuit that uses the General Communication Channel (GCC). In this case, the GCC is part of the ODUk/Optical Transport Unit (OTUk) frame and can derive its timing from the ODUk circuit.
During connection establishment or connection tear down, the timing basis must switch from a local timing source to timing based on timing information in the payload of a packet in the case of connection establishment, and from payload timing to the local timing source in the case of connection tear down. This is referred to as BITS-to-GAPS or GAPS-to-BITS switching, respectively. If the ODUk circuit is switched or replaced by a maintenance signal, a discontinuity in the start-of-frame location, referred to as frame slip, is inevitable. Other discontinuities in the ODUk/OTUk frame can arise from hardware reconfiguration, which occurs to support different signal rates. For example, hardware may be re-configured to support ODUj circuits on ODUk lines.
Discontinuities or frame slips can result in loss of control plane packets or in loss of control plane connectivity. Certain protocols have been introduced to address this problem. These protocols are bi-directional since they must ensure that both ends of an Optical Transport Network (OTN) link are in an operational state and capable of sending and receiving control plane messages. Typically, these protocols require buffering or re-transmission of control plane messages until an acknowledgement is received, or a timer expires. Timers must be set long enough to allow for round trip delay on the OTN link. Current solutions assume a worst case round trip delay or provide a manually settable value for the timer.
Using timer and retry attempts at an application layer results in slower mesh restoration and slower dynamic connection setup time, because they involve using pre-defined timer durations between spans that are longer than necessary. Identifying an accurate timer value is often difficult, so network operators tend to select timers based on worst case delays. Therefore, it is desirable to have a method and system that provides efficient timer implementation.